This disclosure relates generally to integrated circuits having built-in self test (BIST) circuits, and more particularly, to BIST circuits with clock control.
Built-in self test (BIST), which refers to test circuitry on the same integrated circuit as the circuitry being tested, has become a very popular way to assist in testing an integrated circuit during normal testing plus providing effective testing even after the integrated circuit has been placed in a product. BIST allows for testing during normal operation, as well as using test patterns and other test techniques, in the operating environment in which the integrated circuit will spend its life as part of a product. The type of flexibility in the actual operating environment can result in a more effective test and also can be used for testing after a lengthy period of operation in which some aspects of the circuit may have declined. In such case, this can be used for early detection of a problem so that action can be taken before the problem results in a system failure. At the same time it is desirable for the BIST circuit to be efficient so as to not take up too much space and to provide flexibility in providing desirable tests. Even if ultimately the tests are fixed, the development of the tests may benefit from having the ability to be changed without changing the area occupied by the BIST circuitry and to avoid having to otherwise make significant changes to the BIST circuit in the process of finalizing its design.
Accordingly there is a need to improve upon one or more of the issues raised above in the context of BIST.